渤东凹陷南部PL14区T20界面厘定及特征

渤东凹陷南部地区油气资源丰富,但多年勘探一直未获重大发现,其中该区新近系与古近系地层分界面T20的认识不清可能是制约该区油气发现的一个重要因素。本文采用区域控制、单井解析、分类对比的研究思路,综合利用钻井、地震资料,对研究区T20界面进行了重新厘定和界面特征的对比分析。从古生物、岩性组合旋回变化、地层接触关系等方面,认为应将研究区T20界面整体上调至一套振幅较弱的波组之中,钻井上该界面上下古生物种群及数量发生突变,并位于一套进积型准层序组的顶面,地层接触关系表现为顶超特征。研究区T20界面地震反射特征与区域上其他地区存在明显差异,界面上、下地层的岩性、岩相不同于邻区是造成T20界面地震反射特征差异的重要原因。

Determination and characterization of T20 sequence boundary in PL14 in the south of Bodong sag

The south of Bodong sag is abundant in oil and gas resources, but its exploration lacks significant breakthrough, which might be due to unclear understanding of T20, the interface of neogene and paleogene strata. This paper determined and characterized the T20 sequence boundary applying regional control, single well analysis, classification and comparison, combined with seismic and logging data. The results show that the T20 sequence boundary should be raised to a set of weak amplitude wave group according to ancient biological, lithologic composition and stratigraphic contact relationship. The surface boundary was characterized by toplap, and located at the top of retrogradational parasequence set; meanwhile, ancient biological population and quantity were changed between the upper and lower strata. The surface characteristics were different from that of the other areas because of the difference in lithology and lithofacies between the upper and lower strata of the T20 sequence boundary.